How an electrical capacitor works ?

A capacitor consists of two conductive plates with an insulating layer (dielectric) between them. When a capacitor is connected to a DC voltage supply (closing the pushbutton S1 in Figure 3.5), there is a brief flow of charging current, which electrically charges the two plates.

If the connection to the voltage supply is then interrupted (opening the pushbutton S1), the charge remains stored in the capacitor. The greater the capacitance of a capacitor, the more electrically charged particles it stores at the same voltage. The actual size specification for a capacitor is the capacitance C. It is defined as the relationship between the magnitude of charge Q stored in the capacitor and the voltage V applied to the capacitor:

The unit of capacitance is the "farad" (F)

When the electrically charged capacitor is connected to a consuming device (closing the pushbutton S2 in Figure 3.5), charge balancing takes place. An electrical current flows through the consuming device until such time as the capacitor is fully discharged.